Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0433—Nickel- or cobalt-based alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/009—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of turbine components other than turbine blades
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
  • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
  • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
  • F01D5/12—Blades
  • F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/20—Direct sintering or melting
  • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
  • B22F2003/248—Thermal after-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/14—Both compacting and sintering simultaneously
  • B22F3/15—Hot isostatic pressing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y80/00—Products made by additive manufacturing

Definitions

• the present invention relates to a nickel-cobalt-based alloy, a nickel-cobalt-based alloy member using the same, and a method for manufacturing the same.
• a nickel-based alloy is used as a heat-resistant member for an aircraft engine or a power-generating gas turbine, particularly as a turbine disk.
• the heat-resistant member such as the turbine disk is required to have excellent strength such as creep strength and fatigue strength as well as high-temperature oxidation resistance. Therefore, a nickel-based alloy having high-temperature oxidation resistance by adding chromium has been proposed.
• the nickel-based alloy there has been known a nickel-based alloy containing, with respect to the total amount, Cr in a range of 11.5 to 11.9% by mass, Co in a range of 25 to 29% by mass, Mo in a range of 3.4 to 3.7% by mass, W in a range of 1.9 to 2.1% by mass, Ti in a range of 3.9 to 4.4% by mass, Al in a range of 2.9 to 3.2% by mass, C in a range of 0.02 to 0.03% by mass, B in a range of 0.01 to 0.03% by mass, Zr in a range of 0.04 to 0.06% by mass, Ta in a range of 2.1 to 2.2% by mass, Hf in a range of 0.3 to 0.4% by mass, Nb in a range of 0.5 to 0.8% by mass, and the balance Ni and inevitable impurities (see Patent Literature 1).
• the nickel-based alloy there has been known a nickel-based alloy containing, with respect to the total amount, Cr in a range of 11 to 15% by mass, Co in a range of 14 to 23% by mass, Mo in a range of 2.7 to 5% by mass, W in a range of 0.5 to 3% by mass, Ti in a range of 3 to 6% by mass, Al in a range of 2 to 5% by mass, C in a range of 0.015 to 0.1% by mass, B in a range of 0.015 to 0.045% by mass, Zr in a range of 0.015 to 0.15% by mass, Ta in a range of 0.5 to 4% by mass, Hf in a range of 0 to 2% by mass, and Nb in a range of 0.25 to 3% by mass (see Patent Literature 3).
• Non Patent Literature 1 Hiroshi HARADA and Michio YAMAZAKI, "Alloy Design for ⁇ ' Precipitation Hardening Nickel-base Superalloys Containing Ti, Ta, and W", Tetsu-to-Hagane, Vol. 65, pp. 1059-1068 (1979 )
• Non Patent Literature 2 Hidehiro ONODERA, Yoshihito RO, Toshihiro YAMAGATA and Michio YAMAZAKI, "The Effect of Tensile Strength and Ductility on High Temperature Low Cycle Fatigue of Cast Ni-base Superalloys", Tetsu-to-Hagane, Vol. 71, pp. 85-91 (1985 )
• the present applicant has carried out the development of nickel-based alloys of conventional casting (CC) materials, directional solidification (DS) materials, and single crystal (SC) materials that can be used as turbine blades since the 1970s for many years.
• CC conventional casting
• DS directional solidification
• SC single crystal
• a nickel-based alloy having excellent high-temperature characteristics in each of CC materials and SC materials has been successfully developed (for example, JP 3814662 B2 ).
• a heat-resistant member having an excellent temperature capability (a temperature at which a life is 1000 hours at 630 MPa) suitable for turbine disk applications has been successfully developed.
• the developed powder metallurgy (PM) materials and cast and wrought (C&W) materials having similar compositions have excellent temperature capabilities as PM materials and C&W materials, respectively.
• PM materials having a homogeneous structure tend to be mainly used for a turbine disk for a high temperature and high pressure section requiring high reliability. This is because by utilizing a rapid cooling and solidification process in a gas atomized powder manufacturing process, it is possible to design an alloy to which a large amount of heavy elements such as Mo, Hf, Nb, and Ta, which are strengthening elements whose addition amount is limited in C&W materials due to the influence of segregation, are added.
• the temperature capability of the PM materials has improved only by 22°C in 28 years from 693°C (IN100) in 1974 to 715°C (ME3) in 2002 (improvement rate: 0.79°C/year), and further, the addition of Mo, Hf, Nb, Ta, or the like causes a decrease in structure stability, oxidation resistance, and the like. Therefore, in order to further improve engine performance, it is necessary to develop an alloy based on a new design method.
• the present inventors have arrived at the present invention considering that it is possible to significantly improve the temperature capability of an alloy for a turbine disk if the alloy design based on a nickel-based alloy (referred to as a TM alloy) developed by the present applicant for a turbine blade in the 1970s is applied, instead of the conventional high functionality by improving an existing alloy for a turbine disk.
• a TM alloy nickel-based alloy
• the composition of the alloy for a turbine blade is designed assuming use at 900°C or higher, the alloy for a turbine blade tends to be superior in oxidation resistance and corrosion resistance to the alloy for a turbine disk assuming use at 700°C or lower. Therefore, the present inventor has conceived that, if using an alloy for a turbine blade as the base, oxidation resistance and structure stability can be improved by reducing the addition amounts of Mo, Nb, and Hf, and strength enhancement can be achieved by adding elements other than these elements, realization of an alloy for a turbine disk having a significantly improved durable temperature can be expected, and have arrived at the present invention.
• composition elements of the nickel-cobalt-based alloy of the present invention and the content thereof are limited as described above will be described.
• % representing the content is % by mass.
• Co is a component useful for controlling the solvus temperature of the ⁇ ' (gamma prime) phase of nickel-based alloys and nickel-cobalt-based alloys, and an increase in the amount of cobalt decreases the ⁇ ' solvus temperature, increases the process tolerance, and also produces an effect of improving forgeability.
• titanium when titanium is contained in a large amount, it is desirable to add a slightly larger amount of cobalt in order to suppress the TCP phase and improve high-temperature strength.
• the content of cobalt is usually 15% by mass or more and 43% by mass or less, and preferably 15% by mass or more and 35% by mass or less.
• Chromium (Cr) is added for improving environmental resistance and fatigue crack propagation characteristics.
• the content of chromium is 6% by mass or more and 12% by mass or less, preferably 7% by mass or more and 12% by mass or less, and more preferably 8% by mass or more and 12% by mass or less.
• Tungsten (W) is an element that is dissolved in the ⁇ phase and the ⁇ ' phase, strengthens both phases, and is effective for improving high-temperature strength.
• W is an element that is dissolved in the ⁇ phase and the ⁇ ' phase, strengthens both phases, and is effective for improving high-temperature strength.
• the content of W is less than 3% by mass, sufficient improvement in high-temperature strength cannot be obtained.
• the content of W exceeds 9% by mass, high-temperature corrosion resistance may be deteriorated. Therefore, the content of tungsten is 3% by mass or more and 9% by mass or less, preferably 5.5% by mass or more and 8.5% by mass or less, and more preferably 6% by mass or more and 8% by mass or less.
• Aluminum (Al) is an element that promotes the formation of the ⁇ ' phase, and the amount of the ⁇ ' phase is adjusted mainly by the content of aluminum.
• the content of aluminum is 1% by mass or more and 6% by mass or less, and preferably 2% by mass or more and 4% by mass or less.
• the content ratio of titanium and aluminum is strongly related to the generation of the ⁇ phase as a harmful phase, it is preferable to increase the content of aluminum as much as possible in order to suppress this ⁇ phase.
• aluminum is a source material for forming aluminum oxide on the surface of a nickel-based heat-resistant superalloy, and also contributes to improvement in oxidation resistance.
• Titanium (Ti) is a desirable additive element for strengthening the ⁇ ' phase and leading to strength improvement, and combined addition with cobalt realizes a nickel-based alloy and a nickel-cobalt-based alloy having excellent phase stability and high strength.
• a cobalt-titanium alloy for example, Co-12.5% by mass Ti used in Examples described later
• the content of titanium is usually 1% by mass or more and 8% by mass or less, preferably 4% by mass or more and 7% by mass or less, and more preferably 4% by mass or more and 6.1% by mass or less.
• Tantalum (Ta) mainly substitutes Al sites of the ⁇ ' phase to contribute to precipitation strengthening.
• the content of tantalum exceeds 7% by mass, a ⁇ phase or a ⁇ phase as a harmful phase is formed, and the high-temperature strength tends to decrease. Therefore, the content of tantalum is 7% by mass or less, and when the content of tantalum is less than 1.7% by mass, precipitation strengthening is often insufficient, and therefore the content of tantalum is preferably 1.7% by mass or more and 7% by mass or less.
• Carbon (C) is an element effective for improving ductility and creep characteristics at a high temperature. Usually, the content of carbon is 0.01% by mass or more and 0.15% by mass or less.
• Boron (B) can improve creep characteristics, fatigue characteristics, and the like at a high temperature.
• the content of boron is 0.01% by mass or more and 0.15% by mass or less.
• creep strength may be decreased or process tolerances may be narrowed.
• Zirconium is an element effective for improving ductility, fatigue characteristics, and the like. Usually, the content of zirconium is 0.01% by mass or more and 0.15% by mass or less.
• Molybdenum (Mo) has an effect of mainly strengthening the ⁇ phase and improving creep characteristics.
• Molybdenum is an element having a high density, and therefore when the content of molybdenum is too large, the density of the nickel-based alloy and the nickel-cobalt-based alloy increases, which is not practically preferable.
• the content of molybdenum is less than 1.5% by mass.
• Niobium (Nb) is effective as a strengthening element contributing to reduction in specific gravity, but when the content thereof is increased to some extent, there is a possibility that generation of a harmful phase or hot cracking occurs at a high temperature.
• the content of niobium is 5% by mass or less.
• Hafnium (Hf) is a grain boundary segregating element, and segregates at a crystal grain boundary to strengthen the grain boundary, thereby improving high-temperature strength.
• the content of hafnium exceeds 2% by mass, local melting may be caused to reduce the high-temperature strength, which is not preferable. Therefore, the content of hafnium is 2% by mass or less.
• Vanadium (V) is an element that mainly forms a solid solution in the ⁇ ' phase and strengthens the ⁇ ' phase.
• the content of V is preferably 0.5% by mass or less. This is because when the content of V exceeds 0.5% by mass, the creep strength is lowered.
• Silicon (Si) may improve oxidation resistance as a protective film by forming a SiO 2 film on an alloy surface, and may also improve TMF characteristics by suppressing generation of micro cracks from the alloy surface.
• the content of silicon is 0.1% by mass or less. When the content exceeds 0.1% by mass, the solid solubility limit of other elements is lowered, and therefore required thermo-mechanical fatigue (TMF) characteristics and creep characteristics cannot be obtained.
• Calcium (Ca), yttrium (Y), and a lanthanoid elements all enhance the adhesion of a Cr 2 O 3 protective film and an Al 2 O 3 protective film on the alloy surface, and particularly enhance oxidation resistance during repeated oxidation. Therefore, these elements may be contained as necessary. However, when the content of these elements is excessive, inclusions such as oxides increase, and hot workability and weldability deteriorate. Therefore, the content of calcium is 0.05% or less, and the contents of yttrium and the lanthanoid element are both 0.2% or less.
• V, Si, Ca, Y, and the lanthanoid element described above can be contained alone, or two or more thereof can be contained in combination.
• the nickel-cobalt-based alloy of the present invention it is possible to prolong the life of a member used in a high-temperature environment such as a gas turbine member and to improve the efficiency of a gas turbine main body or the like by using the member in a more severe environment, and application to a hydrogen mixed combustion/hydrogen gas turbine, an ammonia mixed combustion gas turbine or the like that is planned in the future is also expected.
• SC materials having a composition in which C, B, and Zr as grain boundary strengthening elements were removed from each alloy composition were cast in a directional solidification furnace and used.
• the cast single crystal sample material round bar (10 mm diameter, 130 mm length) was subjected to a solution treatment at 1200 to 1300°C for 5 hours, and further subjected to an aging heat treatment at 870°C for 20 hours. After the heat treatment, a test piece for a tensile creep test (comparative evaluation test) was prepared from each single crystal sample material round bar.
• powders were prepared by a confined gas atomizing device with some of the example alloys and some of the comparative alloys, and powders having 53 ⁇ m or less particle size were classified and subjected to hot isotropic press (HIP) at 1100°C after sealing to obtain a sintered body.
• HIP hot isotropic press
• Fig. 1 shows the yield of the powder having 53 ⁇ m or less particle size used for sintering. In all of the example alloys, fine powders with more than 70% yield of the powder having 53 ⁇ m or less particle size was manufactured.
• Fig. 2 shows an example of the relative density of HIP materials of the prepared base alloy and example alloy. It is apparent that a good high-density sintered body was obtained in both base alloy 1 and example alloy 2 shown in Fig. 2 .
• Fig. 4 is inverse pole figure orientation maps (IPF maps) showing microstructures before extrusion processing (after heat treatment) and after extrusion processing of example alloy 2 and example alloy 5.
• the "average grain size" in Fig. 4 means an average value of crystal grain sizes.
• Data acquisition by an electron back scattered diffraction pattern (EBSD) method was performed by model TEAM TM EDS (manufacturer name: EDAX Division, AMETEK, Inc.).
• IPF analysis was performed by a software model OIM ver. 8.1.0 (manufacturer name: TSL Solutions K.K.).
• IPF maps of Fig. 4 in both of example alloy 2 and example alloy 5, relatively uniform fine grains were formed after extrusion processing, and internal cracks and the like were not confirmed.
• a prior particle boundary (PPB) causing a decrease in strength was eliminated.
• PPB prior particle boundary
• example alloy 2 Process technique development using vacuum melting, homogenization heat treatment, groove roll, swaging, solution heat treatment, and aging heat treatment was performed on example alloy 2.
• comparative alloy 2 which is a current C&W material, was also manufactured. Plastic working was performed under a preheating condition of 1100°C to prepare swaged materials. The prepared swaged materials of example alloy 2 and comparative alloy 2 were subjected to solution heat treatment at 1160°C and 1100°C/4h/AC, respectively. Further, a two-step aging heat treatment of 650°C/24h/AC + 760°C/16h/AC was performed.
• a sample heat-treated at 870°C/20h which is a standard aging condition of a single crystal model alloy, was also prepared.
• Fig. 6 is scanning electron microscope (SEM) photographs showing results of structure observation of some of the example alloys aged for a long time (3000 hours), showing cases of aging temperatures of 650, 750, and 850°C for each of base alloy 1 and example alloys 1 to 4.
• Fig. 7 is scanning electron microscope (SEM) photographs showing results of structure observation of some of comparative alloys aged for a long time (3000 hours), showing cases of aging temperatures of 650, 750, and 850°C for each of comparative alloy 4 and comparative alloy 5.
• measurement results of precipitates harmful to strength (TCP phase, beta phase, Laves phase, and the like) precipitated in a structure stability test at an aging temperature of 850°C and an aging time of 3000 hours are shown in Table 2.
• example alloys that do not contain Mo, Nb, and Hf and in which the addition amount of Ta is smaller than that of the current material, are a very promising alloy system.
• the base alloy precipitation of a TCP phase and a beta phase was confirmed in base alloy 1 aged at 850°C.
• example alloys 1 to 5 in which Co-12.5% by mass Ti is added to base alloy 1, the contents of Ta and W relatively decrease due to an increase in the contents of Co and Ti as compared with base alloy 1, and thus the structure stability is improved. From the above, it is concluded that particularly example alloys 1, 2, 3, and 4 exhibit excellent structure stability in the operation temperature range for turbine disk applications.
• the nickel-cobalt-based alloy of the present invention preferably has a characteristic in which precipitates harmful to strength are not precipitated in an amount of 1.0% by volume or more, preferably precipitated in an amount of 0.5% by volume or less, and more preferably precipitated in an amount of 0.1% by volume or less in a structure stability test at 850°C for 3000 hours.
• Fig. 8 is a graph showing results of tensile creep tests for base alloys and comparative alloys.
• comparative alloy 1 had the shortest life, and the rupture life was 0.42 h.
• the rupture life is in the order of comparative alloy 3 > comparative alloy 5 > comparative alloy 2 > comparative alloy 4 > comparative alloy 1, and from this result, it is found that comparative alloy 3 and comparative alloy 2, which are nickel-cobalt-based alloys, exhibit excellent creep characteristics.
• base alloy 1 and base alloy 2 exhibited extremely excellent creep characteristics as compared with the comparative alloys.
• Fig. 9A is a graph showing results of creep rupture tests at 800°C and 375 MPa for each of base alloys 1 and 2 and example alloys 1 to 7.
• example alloy 5 in which Co-12.5% by mass Ti and Al were added to base alloy 1, a decrease in life caused by the remaining portion of the eutectic ⁇ ' phase was observed.
• example alloys 6 and 7 in which Co-12.5% by mass Ti was added to base alloy 2 the life tended to be prolonged as the addition amount of Co-12.5% by mass Ti was increased.
• Fig. 10A is a graph showing creep characteristics for cast and wrought materials of example alloy 2 and comparative alloy 2, which are overall curves up to a region where the creep strain exceeds 5%.
• Fig. 10B shows a curve obtained by enlarging a region in Fig. 10 A , where the creep strain is up to 1%.
• Fig. 10A shows a creep temperature capability based on the creep time to rupture in the creep rupture test results at 725°C and 630 MPa.
• the creep temperature capability of comparative alloy 2 is 698°C, whereas that of the 870°C aged material of example alloy 2 is 728°C, and that of the two-step aged material of example alloy 2 is 739°C.
• Fig. 10A is a graph showing creep characteristics for cast and wrought materials of example alloy 2 and comparative alloy 2, which are overall curves up to a region where the creep strain exceeds 5%.
• Fig. 10B shows a curve obtained by enlarging a region in Fig. 10
• 10B shows a creep temperature capability based on the creep time at which the creep strain is 0.2% in the creep rupture test results at 725°C and 630 MPa.
• the creep temperature capability of comparative alloy 2 is 727°C, whereas that of the 870°C aged material of example alloy 2 is 740°C, and that of the two-step aged material of example alloy 2 is 766°C.
• example alloy 2 exhibited the highest temperature capability in the world at the present stage as a cast and wrought material. As described above, the temperature capability of the PM materials has improved only by 22°C in 28 years from 693°C (IN100) to 715°C (ME3) from 1974 to 2002, which is an improvement rate of 0.79°C/year. Example alloy 2 has an improved temperature capability of 24°C as compared to ME3. From this, it is concluded that the design guideline of a novel nickel-cobalt-based alloy using an alloy for a turbine blade as a base alloy is extremely effective as a technique for significantly improving the temperature capability while maintaining the manufacturability of gas turbine disks.
• example alloys 1 to 5 in which Co-12.5% by mass Ti is added to base alloy 1 exhibits a 0.2% proof stress higher than that of base alloy 1 except for example alloy 4.
• the 0.2% proof stress refers to a stress value when the strain reaches 0.2% when a test is performed at a specified temperature and a strain rate of 10 -5 (/s).
• the 0.2% proof stresses at 725°C and 800°C were 980 MPa and 780 MPa, respectively.
• example alloy 1 the 0.2% proof stresses at 725°C and 800°C were 1100 MPa and 930 MPa, respectively.
• the 0.2% proof stresses at 725°C and 800°C were 1080 MPa and 890 MPa, respectively.
• example alloy 3 the 0.2% proof stresses at 725°C and 800°C were 990 MPa and 795 MPa, respectively.
• example alloy 4 the 0.2% proof stresses at 725°C and 800°C were 950 MPa and 750 MPa, respectively.
• example alloy 5 the 0.2% proof stress at 800°C is 880 MPa, and no data is acquired for 725°C.
• the 0.2% proof stresses of these example alloys significantly increased with an increase in the amount of Co-12.5% by mass Ti added to a base alloy, and then gradually decreased. It is considered that the alloy having the maximum strength is present between example alloy 1 and example alloy 2 following the design guideline of this example based on base alloy 1.
• the increase in 0.2% proof stress up to example alloy 1 is considered to be an effect due to the increase in the volume fraction of precipitated phase and the Ti content.
• the gradual decrease from example alloy 2 to example alloy 4 is considered that the contents of Cr and W, which are main solid solution strengthening elements of the alloy matrix, decreased by the addition of Co-12.5% by mass Ti to base alloy 1.
• Fig. 13 shows, as an example, results of weight increasing of example alloys 1, 2, 3, and 4.
• the oxidation resistance is decreased. This decrease is considered to be caused by a decrease in the content of Al or Cr forming an oxide film.
• the oxidation resistance of these example alloys is not inferior to that of comparative alloy 4, which is a commercial alloy, and it is considered that there is no problem in practical use.
• the example alloys exhibit excellent creep strength, temperature capability, and compressive strength as compared with the comparative alloys, and have sufficient oxidation resistance, and it was confirmed that the alloy for a turbine disk can be improved based on a new design method based on an alloy for a turbine blade proposed by the present inventor.
• billets having a homogeneous microstructure can be manufactured by either a casting process or a powder metallurgy process, and manufacturability at an industrial level was confirmed.
• the nickel-cobalt-based alloy of the present invention it is possible to prolong the life of a member used in a high-temperature environment such as a gas turbine member and to improve the efficiency of a gas turbine main body or the like by using the member in a more severe environment, and application to a hydrogen mixed combustion/hydrogen gas turbine, an ammonia mixed combustion gas turbine or the like that is planned in the future is also expected.

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• 2023
  • 2023-10-07 EP EP23888401.9A patent/EP4616976A1/fr active Pending
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